9.2 Revised Total Coliform Rule (RTCR)

9.2 Revised Total Coliform Rule (RTCR)

Quick Answer: The Revised Total Coliform Rule (RTCR), effective April 2016, replaced the 1989 Total Coliform Rule. It uses total coliform as an indicator of potential pathway contamination, not a direct health risk. Any total coliform-positive (TC+) routine sample triggers 3 repeat samples within 24 hours, taken at the original tap and within 5 service connections upstream and downstream. The rule shifts from a strict MCL to a find-and-fix approach: Level 1 and Level 2 assessments identify sanitary defects. An E. coli MCL violation is acute and requires Tier 1 public notification within 24 hours.

Why Coliform Instead of Pathogens

Pathogens like Giardia, Cryptosporidium, norovirus, and pathogenic E. coli are hard to grow in the lab, slow to detect, and present intermittently. Total coliform bacteria are easy to grow, survive longer in water, and die off faster than most pathogens — so their presence signals a sanitary defect that may also let pathogens in. The RTCR treats a coliform-positive as a trigger to investigate and fix, not as proof of disease.

Routine Sampling Schedule

Each system writes a sample siting plan approved by the state that identifies routine sample taps across the distribution system. Frequency depends on population and source type:

• Large community systems typically sample monthly at multiple sites based on population.
• Small groundwater systems serving ≤1,000 people may sample quarterly if sanitary surveys are clean.
• Samples are collected from regular, representative distribution taps (not the treatment plant clearwell).

If a system fails to collect a routine sample, that itself is a monitoring violation.

TC+ Trigger: The 3-Repeat Rule

When a routine sample is total coliform-positive, the system must collect 3 repeat samples within 24 hours of being notified:

1. One at the original tap.
2. One within 5 service connections upstream.
3. One within 5 service connections downstream.

For groundwater systems, the rule also requires triggered source-water monitoring (a raw-water sample at each well in use) because a TC+ in distribution may indicate the source is compromised.

The system must also collect additional routine samples the following month — typically 3 times the normal monthly count — to confirm the system is back in control. This is called increased monitoring.

Assessments: Find and Fix

The RTCR replaces the old MCL (which counted the percentage of positive samples) with assessments that require the system to identify the sanitary defect and correct it.

Both assessments end with a corrective action — repair the break, flush the main, replace the tap, adjust chlorine — and a report to the state.

E. coli MCL = Acute Violation

The RTCR sets an E. coli MCL that is an acute violation. A system hits it when E. coli-positive results occur in any combination of routine or repeat samples (specific trigger patterns are defined in the rule). Because E. coli indicates fecal contamination, this is treated as an acute MCL violation requiring:

• Tier 1 public notification within 24 hours (radio, TV, hand delivery, posting).
• Consultation with the state.
• Likely a boil-water advisory until the system is confirmed safe.
• A Level 2 assessment.

A plain total coliform-positive (without E. coli) is not an acute violation — it triggers repeats and an assessment, but Tier 1 is not required.

Distribution Operator Role

For a Class I operator the RTCR is one of the most frequently tested rules because everything happens in distribution:

• Pull routine samples on schedule from the approved siting plan.
• Recognize a TC+ result and know to collect the 3 repeats within 24 hours in the right locations.
• Maintain a chlorine residual (most systems) so the sampler can record a residual with each coliform sample.
• Keep the sample siting plan current and rotate taps as required.

Exam Tip

Two numbers show up repeatedly on RTCR questions: 3 repeat samples and 24 hours. The 5-connections-upstream-and-downstream pattern is the spatial requirement. And remember: a TC+ alone is a Level 1 trigger; E. coli is the acute Tier 1 trigger.